For each of the following scenarios, state the independent variable and the dependent  variable.
a. A study is done to determine if younger mountain climbers are involved in more  accidental deaths. The death rate per 100,000 is compared to the age of climbers.
b. A study is done to determine if the monthly electricity bill changes is based on the  number of family pets.
c. Insurance companies calculate auto insurance premiums partially on the number of  previous insurance claims of the applicant.